1. Field of the Invention
The present invention relates generally to the field of ophthalmology and, more specifically, to the field of eyelid hygiene and treatment.
2. Description of the Related Art
This section is intended to introduce the reader to aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In the field of ophthalmology, a common patient complaint is of ocular irritation, such as dry-eye, a diagnosis characterized by burning, red eyes, irritation, itching, and vision fluctuations. Symptoms typically result from an insufficiently lubricated ocular surface which increases the shear forces associated with blinking and which reduces the ability of the ocular surface to respond to environmental challenges, such as wind, low humidity, and particulates. The label “dry-eye,” however, may be a misnomer as aqueous tear production can be normal in patients with this diagnosis. Instead, dry-eye symptoms are commonly precipitated by a change in the composition of the tear film coating of the eye that may be in itself irritating or that may deviate from the tear film's optimal ocular surface properties, causing an increase in the rate of evaporation of the tear film.
In particular, a lipid component of the tear film may be either reduced or changed in composition, thereby increasing the rate of evaporation. These changes in the lipid layer are often the result of obstructive meibomian gland dysfunction (MGD), a form of posterior blepharitis that results in changes to the local eyelid margin. In particular, obstruction of the meibomian glands may decrease delivery of meibomian gland secretions, which comprise various oil and lipid components and which are typically expelled from the glands upon blinking.
The meibomian glands themselves are a row of enlarged sebaceous glands disposed along the lid margin posterior to the lid lashes. The meibomian glands are found on both the upper and lower lids and produce a holocrine lipid secretion that constitutes the surface layer of the preocular tear film. This lipid surface layer helps produce a smooth optical surface, reduces evaporation, and reduces contamination by skin surface lipids. Despite its importance, the lipid surface layer is believed to comprise only the upper 70 nanometers or so of the 7.0 micron thick tear film.
Structurally, the meibomian glands are generally straight tubules from which saccular acini project. Smooth and skeletal muscle fibers and elastic tissue is found around the acini. In addition, the muscle of Riolan and other periocular skeletal eye muscles are also associated with the glands. Fibers in the muscle of Riolan are arranged around the ducts leading to the orifices of the Meibomian glands and are believed to have a role in the expression of the meibomian gland secretions. In particular, combined movements within the Riolan muscle may compress the meibomian gland ductules, expressing their contents. The periocular eye muscles maintain line tone and the normal apposition of the eyelid margins to the ocular surface providing optimal application of the components of the tear film.
However, when a patient is afflicted with MGD, the meibomian glands may be plugged or partially plugged, typically with yellowish, solidified oil and lipids. In particular, the gland products themselves, i.e. lipids and oils, may solidify within the gland ducts plugging the ducts. Due to the plugging of the ducts, secretory product, as well as the relative bacterial counts, are built up within the gland and sufficient meibomian oils and lipids are not expressed into the tear film, increasing the relative counts of the normal flora of the eye. The solidification of gland products may occur for various reasons such as temperature sensitivity or melting point shifts, hormonal influences, variations in lipid composition, or infection.
Treatment for MGD comprises a regimen of lid hygiene. Typically applying warm compresses to the eyelids, massaging the eyelids, and washing the eyelid using a lid scrub are performed to express the contents of the meibomian glands. While such a regimen may be helpful, it may not be sufficient in acute cases of MGD. In addition, depending on the indications, antibiotics and steroids might also be employed in treatment. A more effective mechanism of lid hygiene, capable of unplugging even severely plugged ducts is therefore desired. The present invention addresses one or more of the concerns set forth above.